JP2008295737A - Magnetic field coil, and magnetic resonance imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an RF coil by which a high-frequency magnetic field having two kinds of magnetic resonant frequencies which have frequencies being close to each other is highly efficiently and evenly irradiated, and which can receive two kinds of magnetic resonant signals which have frequencies being close to each other by a high sensitivity and an even sensitivity distribution, in an MRI device. <P>SOLUTION: A plurality of frequencies which are tuned are adjusted in such a manner that they may become values between resonant frequencies of series resonant circuits which constitute the RF coil. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a magnetic resonance imaging (MRI) apparatus, and more particularly to a magnetic field coil, particularly a radio frequency (RF) coil, used in an MRI apparatus that captures nuclear magnetic resonance images of a plurality of nuclides.

The MRI apparatus is a medical image diagnostic apparatus that causes magnetic resonance to occur in nuclei in an arbitrary cross section that crosses an examination target, and obtains a tomographic image in the cross section from a generated magnetic resonance signal. In general, a magnetic resonance signal of a hydrogen nucleus ( ¹ H) is used.

MRS (Magnetic Resonance Spectroscopy) and MRSI (Magnetic Resonance Spectroscopic Imaging), which are a kind of magnetic resonance imaging methods, are used as methods for measuring the metabolic state in a living body. Here, MRS is a method of measuring the frequency distribution of a magnetic resonance signal emitted from a substance, and MRSI is a method of imaging based on a specific frequency component of a magnetic resonance signal having a frequency distribution. . In these imaging methods, in addition to imaging by magnetic resonance signals of hydrogen nuclei ( ¹ H), fluorine ( ¹⁹ F), phosphorus ( ³¹ P), sodium ( ²³ Na), carbon ( ¹³ C), etc. other than hydrogen Nuclear magnetic resonance signals are also imaged. To obtain images of magnetic resonance signals of two different nuclei at the same time, the RF coil that irradiates a high-frequency magnetic field that excites the nuclei and detects the magnetic resonance signal is set to the frequency of the magnetic resonance signals of the two nuclei (magnetic resonance). Frequency). Such a coil is called a double-tuned RF coil.

As shown in FIG. 20, a conventional double-tuned RF coil includes a coil loop in which a trap circuit in which an inductor and a capacitor are connected in parallel is inserted (see, for example, Patent Document 1 and Non-Patent Document 1). ). These double-tuned RF coils assume that the frequencies of two magnetic resonance signals are separated from each other, for example, when ¹ H and ³¹ P are tuned, and the two frequencies to be tuned are close to each other It is not supposed to be used for In order to realize double tuning of two frequencies close to each other using these double tuning RF coils, the value of the inductor used for the trap circuit must be 10 nH or less and the value of the capacitor must be several hundred pF or more. There is. An inductor having a small value is difficult to manufacture and has almost no adjustment range, which is unrealistic. On the other hand, a capacitor having a large value cannot ignore the high-frequency loss of the element itself at 1 MHz or more, leading to a decrease in RF coil reception sensitivity and transmission efficiency.

  The double-tuned RF coil used when the two magnetic resonance frequencies are close to each other is a saddle-type double-tuned RF coil in which two saddle-shaped RF coils that resonate with the respective frequencies are arranged orthogonal to each other (see FIG. 21). ), There is a double-tuned RF coil in which the value of the capacitor of the birdcage RF coil is partially changed to resonate the coil at each frequency (for example, see Non-Patent Document 2).

JP-A-6-242202 M.M. D. Schnall et al., “A New Double-Tuned Probe for Current 1H and 31P NMR” for simultaneous detection of 1H · 31P nuclear magnetic resonance signals, Journal of Magnetic US, Journal of Magnetic US 1985, 65, p. 122-129 Peter M. Joseph et al., “A Technique for Double Resonant Operation of Birdcage Imaging Coils”, I E E Transactions on E on Medical Imaging), 1989, 8, p. 286-294

  The saddle-type double-tuned RF coil and the birdcage-type double-tuned RF coil have different sensitivity distributions of the coils corresponding to the two types of magnetic resonance signals, so there is a region where good sensitivity can be obtained for both signals. Limited. In addition, these double-tuned RF coils cannot employ a QD (quadture) method in which the sensitivity is improved by 1.4 times, and sufficient sensitivity cannot be obtained.

  The present invention has been made in view of the above circumstances. In an RF coil of an MRI apparatus, a high-frequency magnetic field having a plurality of magnetic resonance frequencies close to each other is irradiated with high efficiency and uniformity, and a magnet having these frequencies. It is an object of the present invention to provide a technique for receiving a resonance signal with high sensitivity and uniform sensitivity distribution.

  The RF coil of the MRI apparatus of the present invention is characterized in that a plurality of frequencies to be tuned are adjusted to be between resonance frequencies of a plurality of series resonance circuits constituting the RF coil.

  Specifically, a first series resonant circuit in which a capacitor is inserted in a loop coil made of a conductor, a first circuit connected in parallel to the first series resonant circuit, and a parallel connection to the first circuit A magnetic field transmission / reception coil of a magnetic resonance imaging apparatus including a signal processing circuit, wherein the first circuit includes a capacitor and an inductor, and a plurality of series resonance circuits having different resonance frequencies are connected in parallel, and each series The resonance frequency of the resonance circuit is different from the resonance frequency of the first series resonance circuit, and each resonance frequency of the magnetic field transmitting / receiving coil is between the resonance frequencies of the first series resonance circuit and the series resonance circuit. Provided is a magnetic field transmitting / receiving coil of a magnetic resonance imaging apparatus characterized by being adjusted. Here, the first circuit is a circuit that is connected in parallel to the first series resonance circuit and in which the series resonance circuit is connected in parallel. Further, a plurality of series resonance circuits each having a capacitor and an inductor and having different resonance frequencies are connected in parallel, and the resonance frequency of each series resonance circuit is different from the resonance frequency of the first series resonance circuit.

  According to the present invention, in an RF coil of an MRI apparatus, a high-frequency magnetic field having a plurality of magnetic resonance frequencies whose frequencies are close to each other is irradiated with high efficiency and uniformity, and magnetic resonance signals having these frequencies are highly sensitive and uniform. It can be received with a sensitivity distribution.

<< First Embodiment >>
A first embodiment to which the present invention is applied will be described. First, the overall configuration of the MRI apparatus of this embodiment will be described. FIG. 1 is an overview of the MRI apparatus of this embodiment. In the figure, the z-axis direction of coordinate 9 is the static magnetic field direction. An MRI apparatus 100 shown in FIG. 1A includes a horizontal magnetic field type magnet 101. An MRI apparatus 200 shown in FIG. 1B includes a vertical magnetic field type magnet 201. These MRI apparatuses 100 and 200 include a table 301 on which the inspection object 103 is placed. This embodiment can be applied to both the MRI apparatus 100 including the horizontal magnetic field type magnet 101 and the MRI apparatus 200 including the vertical magnetic field type magnet 201. Hereinafter, the MRI apparatus 100 having the horizontal magnetic field type magnet 101 will be described as an example.

  FIG. 2 is a block diagram showing a schematic configuration of the MRI apparatus 100. As shown in the figure, an MRI apparatus 100 includes a horizontal magnetic field type magnet 101, a coil 102 that generates a gradient magnetic field, a sequencer 104, a transmission / reception RF coil 116 that generates a high-frequency magnetic field and receives a signal from an inspection object 103. Is provided. The gradient coil 102 is connected to a gradient power source 105. The transmission / reception RF coil 116 is connected to the high-frequency magnetic field generator 106 and the receiver 108. The sequencer 104 sends commands to the gradient magnetic field power source 105 and the high frequency magnetic field generator 106 to generate a gradient magnetic field and a high frequency magnetic field, respectively. The high frequency magnetic field is applied to the inspection object 103 through the transmission / reception RF coil 116. An RF signal generated from the inspection target 103 by applying a high-frequency magnetic field is detected by the transmission / reception RF coil 116 and detected by the receiver 108. The magnetic resonance frequency used as a reference for detection by the receiver 108 is set by the sequencer 104. The detected signal is sent to the computer 109 through an A / D conversion circuit, where signal processing such as image reconstruction is performed. The result is displayed on the display 110. The detected signals and measurement conditions are stored in the storage medium 111 as necessary. The sequencer 104 performs control so that each device operates at a timing and intensity programmed in advance. Further, when it is necessary to adjust the static magnetic field uniformity, the shim coil 112 is used. The transmission / reception RF coil 116 may be provided separately with a transmission coil that generates a high-frequency magnetic field and a reception coil that receives a signal from the inspection target 103, or may be used as a single coil. Hereinafter, in this embodiment, a case where a single coil is also used will be described as an example.

The transmission / reception RF coil 116 of this embodiment operates as a double-tuned RF coil. FIG. 3 is a circuit diagram of a double-tuned loop coil 150 used as the transmission / reception RF coil 116 of the present embodiment. The z-axis direction of coordinate 9 in the figure is the static magnetic field direction. The double-tuned loop coil 150 of this embodiment includes a first series resonance circuit 41 in which eight inductors 19 and seven capacitors 29 are alternately connected in series, and a capacitor 22 (the value of the capacitor 22 is C _B. The same applies hereinafter) and a second series resonant circuit 42 in which an inductor 12 (L _B ) is connected in series, and a third series in which a capacitor 23 (C _C ) and an inductor 13 (L _C ) are connected in series. A resonance circuit 43 and a signal processing circuit 45 are provided. The first series resonance circuit 41, the second series resonance circuit 42, and the third series resonance circuit 43 are connected in parallel in this order, and the signal processing circuit 45 is connected in parallel to the third series resonance circuit 43. The The double-tuned loop coil 150 of this embodiment is connected to the high-frequency magnetic field generator 106 and the receiver 108 via the signal processing circuit 45. The signal processing circuit 45 is a circuit including a circuit for processing a signal such as a balun circuit or an impedance conversion circuit, and may further include a signal amplifier.

Here, the inductor 19 represents an inductor component per one when the loop coil 1 made of a conductor is divided into eight. For example, assuming that the inductance (L _A ) of a typical loop coil is 1 μH, the value of the inductor 19 is 125 nH. Capacitor 29 represents one capacitor when the capacitor (C _A ) inserted in series in loop coil 1 is divided into seven. The number of divisions may be changed depending on the size of the capacitor (C _A ).

Here, the resonance frequencies of the first series resonance circuit 41, the second series resonance circuit 42, and the third series resonance circuit 43 are f _A , f _B , and f _C , respectively. The double-tuned loop coil 150 of the present embodiment adjusts the values of the inductor and the capacitor to thereby adjust the nuclear magnetic resonance frequencies of the two different nuclei (first resonance frequency f ₁ , second resonance frequency f ₂ ; f ₁ <f ₂ ). Therefore, the resonance frequencies f _A , f _B , and f _C of each series resonance circuit are adjusted so as to satisfy the following (Equation 1).

Hereinafter, when the resonance frequency of each series resonance circuit is adjusted according to the above (formula 1), the double-tuned loop coil 150 uses the inductors and capacitors that are the respective constituent elements with realistic values, and the mutual frequency. It will be explained that two types of magnetic resonance signals that are close to each other can be transmitted and received. Here, as an example, of two different nuclear magnetic resonance frequency, a first magnetic resonance frequency f _1, and fluorine nuclear magnetic resonance frequency 120MHz in the static magnetic field strength 3T (Tesla), a second magnetic resonance the frequency f _2, will be described as an example the case of a nuclear magnetic resonance frequency 128MHz of protons in the static magnetic field strength 3T.

First, the operation and characteristics of the double-tuned loop coil 150 of this embodiment will be described using its equivalent circuit. FIG. 4 is a diagram for explaining the operation of the double-tuned loop coil using an equivalent circuit. FIG. 4A is an equivalent circuit 500 of the double tuned loop coil 150 of the present embodiment. In this figure, the inductor 11 (L _A ) has a composite value obtained by connecting eight inductors 19 of the double tuning loop coil 150 in series, and the capacitor 21 (C _A ) has seven capacitors 29 of the double tuning loop coil 150. Are combined values connected in series. The double-tuned loop coil 150 of the present embodiment is connected in parallel to a series resonant circuit in which three series resonant circuits (41 ′, 42, 43) including an inductor and a capacitor are connected in parallel as shown in FIG. This is represented by an equivalent circuit 500 of the above circuit.

Here, the operation of a general series resonant circuit 40 will be described. FIG. 5 is a diagram for explaining the operation of the series resonant circuit 40. As shown in FIG. 5A, the series resonant circuit 40 includes an inductor 15 (L) and a capacitor 25 (C) connected in series. When the frequency of the applied voltage is f and the angular frequency is ω (ω = 2πf), the impedance Z at both ends of the series resonant circuit 40 is expressed by (Equation 2).

ここで、直列共振回路４０の見かけのインダクタンスの値Ｌ’は、（式４）で表される。

一方、直列共振回路４０の共振周波数ｆ_Ｒより低い周波数領域（ｆ＜ｆ_Ｒ）においてインピーダンスＺは（式５）で表され、容量性リアクタンスとして動作する。

ここで、直列共振回路４０の見かけのキャパシタンスの値Ｃ’は（式６）で表される。

とする。 The impedance Z changes as shown in FIG. 5B depending on the frequency f, and resonates at the frequency f = f _R. In FIG. 5B, the impedance Z is expressed by (Equation 3) in a frequency region (f _R <f) higher than the resonance frequency fR of the series resonance circuit 40, and operates as an inductive reactance.

Here, the apparent inductance value L ′ of the series resonant circuit 40 is expressed by (Equation 4).

On the other hand, in a frequency region (f <f _R ) lower than the resonance frequency f _R of the series resonance circuit 40, the impedance Z is expressed by (Equation 5) and operates as a capacitive reactance.

Here, the apparent capacitance value C ′ of the series resonant circuit 40 is expressed by (Equation 6).

And

As described above, the series resonance circuit 40 operates differently at the resonance frequency as a boundary according to the frequency of the applied voltage. The resonance frequencies f _A , f _B , and f _C of the series resonant circuits 41 ′, 42, and 43 of the equivalent circuit 500 of the double tuned loop coil 150 of the present embodiment are adjusted to satisfy (Equation 1). For this reason, when a high-frequency signal having the first resonance frequency f ₁ is applied, the series resonance circuit 41 ′ and the series resonance circuit 43 of the equivalent circuit 500 operate as capacitive reactances (capacitors), and the series resonance circuit 42 is inductive. Operates as a reactance (inductor). The configuration of the equivalent circuit 500 at this time is shown in FIG. As shown in the figure, when a high-frequency signal having the _first resonance frequency frequency f ₁ is applied, the equivalent circuit 500 includes a capacitor 76 (C _A ′), an inductor 73 (L _B ′), and a capacitor 77 (C _C ') Is represented as a parallel resonant circuit 501 connected in parallel.

On the other hand, the case of applying the second high-frequency signal of the resonance frequency the frequency f _2, the series resonant circuit 41 'and the series resonant circuit 42 of the equivalent circuit 500 operates as an inductive reactance (inductor), the series resonant circuit 43 capacitor It operates as a reactive reactance (capacitor). The configuration of the equivalent circuit 500 at this time is shown in FIG. As shown in the figure, when a high frequency signal having the _second resonance frequency frequency f ₂ is applied, the equivalent circuit 500 includes an inductor 74 (L _A ″), an inductor 75 (L _B ″), and a capacitor 78 ( C _C ″) is represented as a parallel resonant circuit 502 connected in parallel.

Accordingly, when the values of the capacitor and the inductor are adjusted so that the resonance frequency of the parallel resonance circuit 501 becomes the first resonance frequency f ₁ and the resonance frequency of the parallel resonance circuit 502 becomes the second resonance frequency f 2, this equivalent circuit is obtained. The double-tuned loop coil 150 of this embodiment represented by 500 resonates at the first resonance frequency f ₁ and the second resonance frequency f ₂ . That is, two types of magnetic resonance signals can be transmitted and received. Hereinafter, adjustment of the values of the capacitor and the inductor will be described.

The values C _A 'C _C ' of the capacitors 76 and 77 of the parallel resonant circuit 501 are expressed by (Expression 7) and (Expression 8) below from (Expression 3). Further, the value L _B ′ of the inductor 73 is expressed by the following (Expression 9) from (Expression 4).

Here, generally, the following relationship exists between the resonant frequency f _0p of the parallel resonant circuit composed of the inductor and the capacitor, the inductor value L, and the capacitor value C.

When the parallel resonance circuit 501 is adjusted to be tuned to the first resonance frequency f ₁ , the resonance frequency of the parallel resonance circuit 501 becomes the first resonance frequency f _1, and therefore, f ₁ and the value C of each capacitor 76, 77 _A ′, C _C ′, and the value L _B ′ of the inductor 73 satisfy (Equation 10). Therefore, the relationship among f ₁ , C _A ′, C _C ′, and L _B ′ is as shown in (Formula 11).

同様に、（式９）、（式７）、（式８）、（式１１）をＣ_Ａ、Ｃ_Ｂ、Ｃ_Ｃについて解くと、キャパシタ２１、２２、２３（Ｃ_Ａ、Ｃ_Ｂ、Ｃ_Ｃ）は、以下の関係を有する。

(Equation 7), (8), (9) and solving the _{L A,} L B, the _{L C} (Equation 11), an inductor _{11,12,13 (L A, L B,} L C) is It has the following relationship.

Similarly, when (Equation 9), (Equation 7), (Equation 8), and (Equation 11) are solved for C _A , C _B , and C _C , capacitors 21, 22, and 23 (C _A , C _B , and C _C ) Has the following relationship:

On the other hand, the values L _A ″ and L _B ″ of the inductors 74 and 75 of the parallel resonant circuit 502 are expressed by the following (Expression 14) and (Expression 15) from (Expression 4). The value C _C ″ of the capacitor 78 is expressed by the following (Expression 16) from (Expression 3).

When adjusting the parallel resonance circuit 502 to tune to the twelfth resonance frequency f ₂ , the resonance frequency of the parallel resonance circuit 502 is the second resonance frequency f ₂ , and therefore, f ₂ and the value L of each inductor 74, 75. _A ″, L _B ″, and the value C _C ″ of the capacitor 78 satisfy (Equation 10). That is, the relationship among f ₂ , L _A ″, L _B ″, and C _C ″ is as shown in (Equation 17).

同様に、（式１４）、（式１５）、（式１６）、（式１７）をＣ_Ａ、Ｃ_Ｂ、Ｃ_Ｃについて解くと、キャパシタ２１、２２、２３（Ｃ_Ａ、Ｃ_Ｂ、Ｃ_Ｃ）は、以下の関係を有する。

When (Equation 14), (Equation 15), (Equation 16), and (Equation 17) are solved for L _A , L _B , and L _C , the inductors 11, 12, and 13 (L _A , L _B , and L _C ) are It has the following relationship.

Similarly, when (Expression 14), (Expression 15), (Expression 16), and (Expression 17) are solved for C _A , C _B , and C _C , capacitors 21, 22, and 23 (C _A , C _B , and C _C ) Has the following relationship:

Accordingly, since the value _L A of each _inductor, L B, the _{L C} that must be met at the same time and (Equation 12) and (Equation 18), an inductor 12 _{(L B)} and the inductor 13 _{(L C),} each resonant Using the frequencies f ₁ , f ₂ , f _A , f _B , f _C and L _A , they are represented by (Equation 20) and (Equation 21), respectively.

On the other hand, since the values C _A , C _B , and C _C of each capacitor need to satisfy (Equation 13) and (Equation 19) at the same time, the capacitor 22 (C _B ) and the capacitor 23 (C _C ) ) And (Equation 19), using the resonance frequencies f ₁ , f ₂ , f _A , f _B , f _C and C _A , respectively, are expressed by (Equation 22) and (Equation 23).

  Using the relationship obtained in the equivalent circuit 500, the value of each capacitor and inductor of the double-tuned loop coil 150 of this embodiment is calculated.

First, the resonance frequency f _A of the series resonance circuit 41 is determined. As described above, here, the first resonance frequency f ₁ is 120 MHz, and the second resonance frequency f ₂ is 128 MHz. Therefore, the resonance frequency f _A of the series resonance circuit 41 is determined between 120 MHz and 128 MHz from (Equation 1). Here, for example, it is set to 124 MHz.

Next, to determine the L _A is the combined value of the inductor of the series resonant circuit 41. Here, for example, the value of the inductor of a typical loop coil is 1 μH. Accordingly, the values of the eight inductors 19 constituting the series resonant circuit 41 are each 125 nH.

本関係を直列共振回路４１にあてはめると、キャパシタの合成値であるＣ_Ａは、１．６５ｐＦとなる。従って、直列共振回路４１を構成する７つのキャパシタ２９の値は、それぞれ１１．６ｐＦとなる。 Next, C _A that is a composite value of the capacitors of the series resonant circuit 41 is determined. Here, in general, in a series resonance circuit, the resonance frequency f _os , the inductor value L, and the capacitor value C have the following relationship (Equation 24).

Applying this relationship to the series resonant circuit 41, _{C A} is the combined value of the capacitor becomes 1.65PF. Therefore, the values of the seven capacitors 29 constituting the series resonance circuit 41 are 11.6 pF, respectively.

Next, to determine the resonant frequency _{f C} of the resonance frequency _{f B} and the series resonant circuit 43 of the series resonant circuit 42. These are determined to satisfy (Equation 1). At this time, the values obtained from (Equation 20), (Equation 21), (Equation 22), and (Equation 23) are such that the inductor value and the inductor value are 10 nH so that the high frequency loss of the inductor and the capacitor is low and adjustment is easy. The value of the capacitor is determined to be between 10 pF and 200 pF between 1 and 200 nH. FIG. 6A shows the frequency regions of f _B and f _C that satisfy (Equation 1). 6B and 6C, the frequencies of f _B and f _C that fall between 10 nH and 200 nH where L _B and L _C obtained by (Expression 20) and (Expression 21) can be actually produced and adjusted. Indicates the area. Similarly, in FIGS. 6D and 6E, the frequency regions of f _B and f _C that fall between 10 pF and 200 pF where C _B and C _C obtained by (Equation 22) and (Equation 23) have relatively low high-frequency loss are shown. Show. FIG. 6 (f) shows frequency regions fb and fc that satisfy all of FIGS. 6 (a) to 6 (e). Any combination of f _B and f _C in this region may be used. Here, for example, f _B = 93.6 MHz and f _C = 156 MHz.

Finally, using the resonance frequencies f ₁ , f ₂ , f _A , f _B , f _C, and L _A , C _A determined as described above, L _B , L _C , C _B , C _C are expressed as 20), (Formula 21), (Formula 22), and (Formula 23). As a result, L _B = 24.5 nH, L _C = 30.7 nH, C _B = 42.6 pF, and C _C = 94.3 pF. This is within the range of the inductor and capacitor values described above.

As described above, the double-tuned loop coil 150 of the present embodiment has L _A = 1 μH, L _B = 24.5 nH, L _C = 30.7 nH, C _A = 1.65 pF, C _B = 42.6 pF, C By adjusting _C = 94.3 pF, resonance occurs at both the nuclear magnetic resonance frequency 120 MHz of fluorine in 3T and the magnetic resonance frequency 128 MHz of hydrogen nucleus in 3T, and the magnetic resonance signals of fluorine and hydrogen nuclei are Send and receive.

  As described above, the double-tuned loop coil 150 of the present embodiment is tuned to two types of magnetic resonance frequencies that are close to each other, and radiates a high-frequency magnetic field having two types of magnetic resonance frequencies with high efficiency and uniformity, Two types of magnetic resonance signals are received with high sensitivity and uniform sensitivity distribution. In addition, two types of magnetic resonance signals whose frequencies are close to each other by an inductor and a capacitor having realistic values, without using a capacitor having a large value with high frequency loss or an inductor having a small value that is difficult to adjust. Realize transmission and reception. For this reason, the high frequency loss by an inductor or a capacitor can be reduced, and the reception sensitivity and transmission efficiency of the RF coil with respect to two types of magnetic resonance signals whose frequencies are close to each other are improved.

  In addition, as can be seen from the above configuration, the double-tuned loop coil 150 of the present embodiment does not include a trap circuit that is not involved in RF coil signal detection in the signal detection coil. For this reason, the uniformity of the sensitivity distribution of the RF coil can be improved without disturbing the sensitivity distribution of the RF coil by the trap circuit.

  Furthermore, by arranging the loop coil 1 of the double-tuned loop coil 150 of this embodiment in close contact with the inspection object 103, it is possible to detect magnetic resonance signals around the close contact portion with high sensitivity.

In the present embodiment, the case where the combination of the first resonance frequency and the second resonance frequency is the nuclear magnetic resonance frequency of fluorine and hydrogen nuclei has been described as an example. However, the combination is not limited to this. However, a combination in which one resonance frequency is within 70% of other resonance frequencies is desirable. For example, fluorine and helium ⁽³ the He), phosphorus ⁽³¹ P) and lithium ⁽⁷ Li), xenon ⁽¹²⁹ Xe) and sodium ⁽²³ Na), xenon ⁽¹²⁹ Xe) and carbon ⁽¹³ C), sodium ⁽²³ Na ) And carbon ( ¹³ C), oxygen ( ¹⁹ O) and heavy water ( ¹ H), and the like. Of course, the combination of nuclei is not limited to this.

  In addition, the shape of 150 of the double tuning loop coil of this embodiment is not restricted to the above. The equivalent circuit may be equivalent to the equivalent circuit 500.

  For example, one part of the loop coil may have the shape of a saddle coil. FIG. 7 shows a double-tuned saddle type coil 151 which is a modification of the double-tuned loop coil of this embodiment. The z-axis direction of coordinate 9 in the figure is the static magnetic field direction. As shown in this figure, the double-tuned saddle coil 151 is connected so that two opposed loops of the saddle type loop coil 1 generate a magnetic field in the same direction, and the surface of each loop is on the side surface of the cylinder. It has a shape deformed along.

  Further, for example, one part of the loop coil may have the shape of a butterfly coil. FIG. 8 shows a double-tuned butterfly coil 152 which is a modification of the double-tuned loop coil of this embodiment. The z-axis direction of coordinate 9 in the figure is the static magnetic field direction. As shown in this figure, the double-tuned butterfly coil 152 has a shape in which two adjacent loops in the same plane of the butterfly loop coil 1 are connected so as to generate magnetic fields in directions opposite to each other. .

  Further, for example, one part of the loop coil may have a solenoid coil shape. FIG. 9 shows a double tuning solenoid coil 153 which is a modification of the double tuning loop coil of this embodiment. The z-axis direction of coordinate 9 in the figure is the static magnetic field direction.

The double-tuned saddle coil 151, the double-tuned butterfly coil 152, and the double-tuned solenoid coil 153 are represented by an equivalent circuit 500. Therefore, the circuit configuration and operation principle are the same as those of the double-tuned loop coil 150. Therefore, the double-tuned saddle coil 151, the double-tuned butterfly coil 152, and the double-tuned solenoid coil 153 are RF coils for two magnetic resonance signals whose frequencies are close to each other, represented by a combination of hydrogen nuclei and fluorine nuclei. Works as. However, since the shape of the coil is different from that of the double-tuned loop coil 150, the values of the inductor 11 (L _A ) and the capacitor 21 (C _A ) of the loop coil change, and accordingly, L _B , L _C , C _B , C _C need to be determined.

  As described above, the double-tuned saddle coil 151, the double-tuned butterfly coil 152, and the double-tuned solenoid coil 153 have a capacitor having a large value with high frequency loss and a small value that is difficult to adjust. Since it is possible to configure an RF coil capable of transmitting and receiving two types of magnetic resonance signals having frequencies close to each other without using an inductor, the high frequency loss due to the inductor and the capacitor can be greatly reduced, and the frequencies close to each other 2 The reception sensitivity and transmission efficiency of the RF coil for various types of magnetic resonance signals are improved. In addition, since the trap circuit not involved in the signal detection of the RF coil is not arranged in the signal detection coil, the sensitivity distribution of the RF coil by the trap circuit is not disturbed, and the uniformity of the sensitivity distribution of the RF coil is improved. Can do.

  Further, since the double-tuned saddle coil 151 has a saddle shape, as shown in FIG. 7, the test object 103 such as the arm, leg, and trunk of the subject is included in the saddle coil. In addition to the surface of the inspection object 103, two types of magnetic resonance signals from the region in the deep direction can be detected with high sensitivity and uniform distribution.

  Since the double-tuned butterfly coil 152 has a butterfly shape, the test object 103 such as the subject's arm, leg, and trunk does not enter the closed space. As shown in FIG. 8, by arranging the inspection object 103 above or below the butterfly coil, two types of magnetic resonance signals from the region in the deep direction of the inspection object 103 are detected with high sensitivity and uniform distribution. Can do.

  Further, since the double-tuned solenoid coil 153 has a solenoid shape, as shown in FIG. 9, the test object 103 such as an arm, a leg, and a torso of the subject is arranged in the solenoid coil. Thus, in addition to the surface of the inspection object 103, two types of magnetic resonance signals from the region in the deep direction can be detected with high sensitivity and uniform distribution. Also, the solenoid coil has a uniform sensitivity distribution over a wider area than the saddle coil.

  In these modifications, one capacitor 21 is installed in the loop coil 1, but a plurality of capacitors may be used.

  In the above-described embodiment and modification, the double-tuned RF coil capable of transmitting and receiving two different types of magnetic resonance signals has been described as an example. However, the number of magnetic resonance signals that can be transmitted and received by the RF coil to which the present invention is applicable is not limited to two. For example, a triple-tuned loop coil capable of transmitting and receiving three different types of magnetic resonance signals may be used.

FIG. 10 shows a triple tuning loop coil 154 which is a modification of the double tuning loop coil of this embodiment. As shown in the figure, in addition to the configuration of the double tuning loop coil 150, the triple tuning loop coil 154 includes a fourth series resonance in which a capacitor 24 (C _D ) and an inductor 14 (L _D ) are connected in series. A circuit 44 is connected in parallel to the third series resonant circuit 43.

The resonance frequency (f _A , f _B , f _C , f _D ) of the first, second, third, and fourth series resonance circuits 41, 42, 43, 44 is set so that the triple-tuned loop coil 154 is the first, In order to resonate at the first, second, and third resonance frequencies (f ₁ , f ₂ , f ₃ ) corresponding to the magnetic resonance frequencies of the second and third elements, the following (Equation 25) is satisfied. Adjust to.

Also in this modification, the values L _B , L _C , and L _{D of the} inductors 12, 13, and 14 and the values C _B , C _C , and C _D of the capacitors 22, 23, and 24 are the values of the double-tuned loop coil 150. Similarly to the case, it is determined by the first, second and third resonance frequencies f ₁ , f ₂ and f ₃ , the combined value L _A of the inductor of the loop coil 1 part, and the combined value C _A of the capacitor.

The operation and characteristics of the triple-tuned loop coil 154 of this modification will be described using an equivalent circuit 600 shown in FIG. The triple-tuned loop coil 154 of this modification is connected in parallel to a series resonant circuit in which four series resonant circuits 41 ′, 42, 43, and 44 are connected in parallel as shown in the figure. This is represented by an equivalent circuit 600 of the above circuit. Resonant frequencies of the respective series resonant circuits 41 ′, 42, 43, and 44 are f _A , f _B , f _C , and f _D.

Since the equivalent circuit 600 is adjusted so as to satisfy (Equation 25), when a high frequency signal having the first resonance frequency f ₁ is applied, the second series resonance circuit 42 operates as an inductive reactance, and the inductor 84 (L _B ′). The first series resonant circuit 41 ′, the third series resonant circuit 43, and the fourth series resonant circuit 44 operate as capacitive reactances, and capacitors 94, 95, and 96 (C _A ′, C _C ′, C _D ′).

Accordingly, the first resonance frequency _{f 1,} the equivalent circuit 600, the inductor 84 shown in FIG. 11 (b), expressed as a parallel resonant circuit 601 connected to the capacitor 94, 95 and 96 in parallel. In this case, adjusting the resonance frequency of the parallel resonant circuit 601 to the first resonance frequency _{f 1,} the equivalent circuit 600, i.e., triple-tuned loop coil 154 resonates at first resonant frequency _{f 1.} Further, the relationship between the first resonance frequency f ₁ and the values of the capacitors 94, 95, 96, C _A ′, C _C ′, C _D ′ and the value L _B ′ of the inductor 84 constituting the parallel resonance circuit 601. Is as follows from (Equation 10).

Further, since the equivalent circuit 600 that is adjusted so as to satisfy (Equation 25), the second high-frequency signal of the resonance frequency f ₂ is applied, first, second series resonant circuit 41 ', 42 induction It can be regarded as inductors 85 and 86 (L _A ″, L _B ″). The third and fourth series resonant circuits 43 and 44 operate as capacitive reactances and can be regarded as capacitors 97 and 98 (C _C ″, C _D ″).

Accordingly, in the second resonance frequency _{f 2,} the equivalent circuit 600, the inductor 85 and 86 shown in FIG. 11 (c), expressed as a parallel resonance circuit 602 connected to the capacitor 97 and 98 in parallel. In this case, adjusting the resonance frequency of the parallel resonant circuit 602 to the second resonance frequency _{f 2,} the equivalent circuit 600, i.e., triple-tuned loop coil 154 resonates at a second resonance frequency _{f 2.} Further, the first resonance frequency f ₁ , the values L _A ″ and L _B ″ of the inductors 85 and 86 constituting the parallel resonance circuit 602, and the values of the capacitors 97 and 98, C _B ″ and C _D The relationship of '' is as follows from (Equation 10).

In addition, since the equivalent circuit 600 is adjusted so as to satisfy (Equation 25), when a high-frequency signal having the third resonance frequency f ₃ is applied, the first, second, and third series resonance circuits 41 ′, 42. , 43 acts as an inductive reactance, the inductor _{87,88,89 (L a ''',} L B''', L C ''') can be regarded as. Similarly, the fourth series resonance circuit 44 at the third resonance frequency f3 operates as a capacitive reactance and can be regarded as a capacitor 99 (C _D ′ ″).

Accordingly, in the third resonant frequency _{f 3,} the equivalent circuit 600, an inductor 87, 88 and 89 shown in FIG. 11 (d), expressed as a parallel resonant circuit 603 connected to the capacitor 99 in parallel. At this time, when the resonance frequency of the parallel resonance circuit 603 is adjusted to the third resonance frequency f ₃ , the equivalent circuit 600, that is, the triple-tuned loop coil 154 resonates at the third resonance frequency f ₃ . Further, the third resonance frequency f ₃ , the values L _A ′ ″, L _B ′ ″, L _C ′ ″ of the inductors 87, 88, 89 constituting the parallel resonance circuit 603, and the value of the capacitor 99, The relationship of C _D ′ ″ is as follows from (Equation 10).

Solving (Equation 26), (Equation 27), and (Equation 28) with respect to L _B , L _C , L _D , C _B , C _C , and C _D , respectively, L _B , L _C , L _D , C _B , and C _{C 1} and _CD are expressed as functions having f _B , f _C , and f _D as variables. f _B , f _C , and f _D satisfy (Equation 25), and the values of the inductor and capacitor are low and high frequency loss is easy to adjust, that is, 10 nH <(L _B , L _C , L _D ) <200 nH By adjusting so that 10 pF <(C _B , C _C , C _D ) <200 pF, the triple-tuned loop coil 154 has three magnetic resonance frequencies (f ₁ , f ₂ , f ₃ ). It can resonate and transmit and receive magnetic resonance signals.

  As described above, the triple-tuned loop coil 154 has two types of magnetic fields whose frequencies are close to each other without using a capacitor having a large value with high frequency loss or an inductor having a small value that is difficult to adjust. Since it is possible to configure an RF coil capable of transmitting and receiving resonance signals, high frequency loss due to inductors and capacitors can be greatly reduced, and RF coil reception sensitivity and transmission efficiency with respect to two types of magnetic resonance signals whose frequencies are close to each other. improves. In addition, since the trap circuit not involved in the signal detection of the RF coil is not arranged in the signal detection coil, the sensitivity distribution of the RF coil by the trap circuit is not disturbed, and the uniformity of the sensitivity distribution of the RF coil is improved. Can do. Furthermore, by arranging the loop coil 1 in close contact with the inspection object 103, it is possible to detect with high sensitivity three types of magnetic resonance signals whose frequencies around the close contact portion are close to each other.

In the above, the resonance frequency (f _A , f _B , f _C , f _D ) of the first, second, third, and fourth series resonance circuits 41, 42, 43, 44 is determined by the triple-tuned loop coil 154. (Equation 25) is satisfied so as to resonate at the first, second, and third resonance frequencies (f ₁ , f ₂ , f ₃ ) corresponding to the magnetic resonance frequencies of the first, second, and third elements. However, the relationship between the resonance frequency of each series resonance circuit 41, 42, 43 and the resonance frequency of the triple tuning loop coil 154 is not limited to this. For _{example, f B <f 1 <f} C <f 2 <f A <f 3 < may be _{f D.}

  Further, quadruple tuning can be achieved by connecting a series resonance circuit in which a capacitor and an inductor are connected in series to the fourth series resonance circuit 44 in parallel. In principle, higher order tuning is also possible.

<< Second Embodiment >>
Next, a second embodiment to which the present invention is applied will be described. The MRI apparatus of this embodiment is basically the same as that of the first embodiment. In the present embodiment, quadrature detection (QD: Quadrature Detection) that improves the irradiation efficiency and the reception sensitivity of the transmission / reception RF coil by combining two of the double-tuned loop coils 150 of the first embodiment with the transmission / reception RF coil 116. ) Method. Hereinafter, a configuration different from the first embodiment will be described.

FIG. 12 is a diagram for explaining the transmission / reception RF coil 116 of the present embodiment, and FIG. 12A is a circuit diagram of the transmission / reception RF coil 116. The z-axis direction of coordinate 9 in the figure is the static magnetic field direction. As shown in the figure, the transmit / receive RF coil 116 of the present embodiment includes a first double-tuned loop coil 61 and a second double-tuned loop coil 62. The configuration of each double-tuned loop coil 61, 62 is the same as that of the double-tuned loop coil 150 of the first embodiment. Further, the first double-tuned loop coil 61 and the second double-tuned loop coil 62 of the present embodiment are respectively similar to the first double-tuned loop coil 150 of the first embodiment. It is adjusted to resonate at the _first and second resonance frequencies f ₂ (> f ₁ ).

  The first double-tuned loop coil 61 and the second double-tuned loop coil 62 of the transmission / reception RF coil 116 of the present embodiment are such that the loop surfaces 171 and 172 of the loop coil portions 1 and 2 are parallel to the z axis, respectively. It is arranged to become. The second double-tuned loop coil 62 is arranged at a position obtained by rotating the first double-tuned loop coil 61 by 90 degrees with the z axis as the rotation axis.

  FIG. 12B is a view of the transmission / reception RF coil 116 as seen from the direction in which the static magnetic field penetrates (z-axis direction in the figure). As shown in this figure, in the transmission / reception RF coil 116 of the present embodiment, the direction 63 of the magnetic field generated by the first double-tuned loop coil 61 and the direction 64 of the magnetic field generated by the second double-tuned loop coil 62 are shown. Is orthogonal. For this reason, the first double-tuned loop coil 61 and the second double-tuned loop coil 62 are not magnetically coupled and operate independently as RF coils for two types of magnetic resonance signals.

  FIG. 13 is a diagram for explaining the connection between the first double-tuned loop coil 61 and the second double-tuned loop coil 62 of the transmit / receive RF coil 116 of the present embodiment, and the high-frequency magnetic field generator 106 and the receiver 108. FIG. The output of the high-frequency magnetic field generator 106 is input to the distributor 50 and divided into two. At this time, distribution is performed so that the phases are orthogonal to each other. The respective outputs are inputted to the port 5 of the first double-tuned loop coil 61 and the port 6 of the second double-tuned loop coil 62 through the balun 46. The outputs from the two double-tuned loop coils 61 and 62 are respectively input to the signal amplifier 47 through the balun 46, and the output of the signal amplifier 47 is input to the combiner 49 through the phase adjuster 48. The output of the synthesizer 49 is input to the receiver 108.

Next, the operation of the transmission / reception RF coil 116 of this embodiment will be described. When a high-frequency signal having the first resonance frequency f ₁ or the second resonance frequency f ₂ is transmitted by the high-frequency magnetic field generator 106, the signal is divided into two signals so that the phase of each signal is orthogonal in the distributor 50. Distributed and applied to port 5 and port 6 through balun 46, respectively. The first double-tuned loop coil 61 and the second double-tuned loop coil 62 are adjusted to resonate at the first resonance frequency f ₁ and the second resonance frequency f ₂ , respectively. The inspection object 103 is irradiated with a high-frequency signal having the first resonance frequency f ₁ or the second resonance frequency f _{2 as} a high-frequency magnetic field. At this time, since the phases of the high-frequency magnetic fields irradiated by the first double-tuned loop coil 61 and the second double-tuned loop coil 62 are orthogonal to each other, the inspection target 103 is centered on the z-axis of the coordinate axis 9. Rotating magnetic field is generated. As described above, the transmission / reception RF coil 116 of the present embodiment realizes QD transmission.

In addition, the first double-tuned loop coil 61 and the second double-tuned loop coil 62 with respect to the magnetic resonance signal having the first resonance frequency f ₁ or the second resonance frequency f ₂ generated from the inspection target 103. Detects signal components that are orthogonal to each other. Each detected signal component is amplified by the signal amplifier 47, processed by the phase adjuster 48, synthesized by the synthesizer 49, and sent to the receiver 108. As described above, the transmission / reception RF coil 116 of the present embodiment realizes QD reception.

  As described above, the transmission / reception RF coil of the present embodiment realizes the QD method, and in addition to the effect produced by the double-tuned loop coil 150 of the first embodiment, a high-frequency magnetic field is applied to the inspection target 103 with high efficiency. Irradiation is possible, and two types of magnetic resonance signals can be detected with higher sensitivity.

  Further, in the above embodiment, the case where two double tuned loop coils 150 of the first embodiment are combined to realize the QD method has been described as an example. However, the coils combined to realize the QD method are not limited to this. For example, two coils are generated, for example, two saddle-type coils are arranged 90 degrees apart from each other with the z-axis as a rotation axis, or a solenoid coil and a saddle coil are arranged so that the cylinders have the same orientation. Any combination of coils that can be arranged so that the magnetic fields are orthogonal to each other is acceptable.

<< Third Embodiment >>
Next, a third embodiment to which the present invention is applied will be described. The MRI apparatus of this embodiment is basically the same as that of the first embodiment. In this embodiment, instead of the transmission / reception RF coil 116 of the first embodiment, a transmission RF coil 116a and a reception RF coil 116b are provided independently. Here, a case where a double-tuned birdcage RF coil having a birdcage shape is used as the transmitting RF coil 116a and a double-tuned loop coil having a loop coil shape is used as the receiving RF coil 116b will be described as an example. . Hereinafter, a description will be given focusing on the configuration different from the first embodiment.

  FIG. 14 is a block diagram for explaining the connection between the RF coil, the high-frequency magnetic field generator 106 and the receiver 108 of the present embodiment. As shown in the figure, the RF coil of the present embodiment includes a double-tuned birdcage RF coil 70 that is an RF coil 116a for transmission, a double-tuned loop coil 71 that is an RF coil 116b for reception, and double-tuned. Magnetic coupling prevention circuits 54 and 68 for preventing magnetic coupling between the birdcage type RF coil 70 and the double tuning loop coil 71, a magnetic coupling prevention circuit driving device 115 for driving the magnetic coupling prevention circuits 54 and 68, and a high frequency And a distributor 50 for distributing the output of the magnetic field generator 106. In this embodiment, the magnetic coupling prevention circuit 54 is inserted in series with the loop portion of the double-tuned birdcage RF coil 70, and the magnetic coupling prevention circuit 68 is inserted in series with the double-tuned loop coil 71.

The double tuned loop coil 71 of this embodiment is configured so that the equivalent circuit is equivalent to the equivalent circuit 500 of the first embodiment, and resonates at the first resonance frequency f ₁ and the second resonance frequency f ₂ . It has been adjusted. The double-tuned birdcage type RF coil 70 is configured by a circuit according to a conventional method, and is adjusted so as to resonate at the first resonance frequency f ₁ and the second resonance frequency f ₂ .

The output of the high-frequency magnetic field generator 106 that generates the high-frequency magnetic field having the first resonance frequency f ₁ is input to the distributor 50 and divided into two, and the respective outputs are input to the pickup coil 65 through the balun 46. The The output of the high-frequency magnetic field generator 106 that generates a high-frequency magnetic field having the second resonance frequency f ₂ is input to the distributor 50 and divided into two, and each output passes through the balun 46 to the pickup coil 66. Entered. The pickup coils 65 and 66 are arranged so as to transmit high frequency signals of the first resonance frequency f ₁ and the second resonance frequency f _{2 to} the double-tuned birdcage RF coil 70, respectively. The double-tuned birdcage RF coil 70 includes a plurality of magnetic coupling prevention circuits 54. A plurality of control signal lines 51 are connected from the magnetic coupling prevention circuit driving device 115 to the magnetic coupling prevention circuit 54. The double-tuned loop coil 71 is disposed inside the double-tuned birdcage RF coil 70 so as to be close to the inspection object 103. The output of the double-tuned loop coil 71 is input to the signal amplifier 47 through the balun 46 and input from the signal amplifier 47 to the receiver 108. A plurality of control signal lines 51 are connected from the magnetic coupling prevention circuit driving device 115 to the magnetic coupling prevention circuit 68.

  FIG. 15A is a diagram for explaining the configuration and arrangement of the double-tuned birdcage type RF coil 70 of the present embodiment. As shown in this figure, in the double-tuned birdcage type RF coil 70 of the present embodiment, two loop conductors 8 are arranged so as to face each other with an axis perpendicular to the loop surface as a common axis. Are connected by a plurality of straight conductors 7 (eight as an example in FIG. 15A). A plurality of magnetic coupling prevention circuits 54 are inserted in the loop conductors 8 respectively. The double-tuned birdcage type RF coil 70 has a cylindrical central axis arranged in parallel to the z-axis direction.

  FIG. 15B is a diagram for explaining the configuration of the magnetic coupling prevention circuit 54 of the present embodiment. As shown in the figure, in the magnetic coupling prevention circuit of this embodiment, a series circuit in which a capacitor 26 and a capacitor 27 are connected in series and an inductor 18 are connected in parallel. The capacitor 26 is connected in parallel with a circuit in which a PIN diode 30 and an inductor 16 are connected in series. The capacitor 27 is connected in parallel with a circuit in which a PIN diode 31 and an inductor 17 are connected in series. Yes. The PIN diode has a characteristic that a value of a direct current flowing in the forward direction of the diode is approximately a certain value and becomes a conductive state, and the on / off of the diode can be controlled by the direct current. The output terminal of the magnetic coupling prevention circuit driving device 115 is connected to a connection point between the PIN diode 30 and the inductor 16 and a connection point between the PIN diode 31 and the inductor 17. By turning on / off the PIN diodes 30 and 31 of the magnetic coupling prevention circuit 54 with the control current 51 from the magnetic coupling prevention circuit driving device 115, the double-tuned birdcage coil 70 is made to transmit the RF coil when transmitting a high frequency signal. It functions as 116a, and when receiving a high-frequency signal, the double-tuned birdcage coil 70 has a high impedance and does not interfere with the reception RF coil 116b (double-tuned loop coil 71). Details of this operation will be described later.

  FIG. 16A is a diagram for explaining the configuration of the double tuning loop coil 71. The z-axis direction of coordinate 9 in the figure is the static magnetic field direction. The double-tuned loop coil 71 of this embodiment is basically the same as the double-tuned loop coil 150 of the first embodiment, and further includes a magnetic coupling prevention circuit 68 in the loop coil 1. In the magnetic coupling prevention circuit 68 shown in FIG. 16B, the capacitor 26 and the capacitor 27 are connected in series. The capacitor 26 is connected in parallel with a circuit in which a PIN diode 30 and an inductor 16 are connected in series. The capacitor 27 is connected in parallel with a circuit in which a PIN diode 31 and an inductor 17 are connected in series. Yes. The PIN diode has a characteristic that a value of a direct current flowing in the forward direction of the diode is approximately a certain value and becomes a conductive state, and the on / off of the diode can be controlled by the direct current. The output terminal of the magnetic coupling prevention circuit driving device 115 is connected to a connection point between the PIN diode 30 and the inductor 16 and a connection point between the PIN diode 31 and the inductor 17. The on / off control is performed by the control current 51 from the magnetic coupling prevention circuit driving device 115. The double tuning loop coil 71 functions as the receiving RF coil 116b when receiving a high frequency signal, and the double tuning loop coil is used when transmitting a high frequency magnetic field. 71 is controlled to have a high impedance so as not to interfere with the transmitting RF coil 116a (double-tuned birdcage coil 70). Details of this operation will be described later.

Immediately before the high-frequency magnetic field having the resonance frequency f ₁ or f ₂ is applied from the high-frequency magnetic field generator 106 to the double-tuned birdcage coil 70, the magnetic coupling prevention circuit driving device 115 performs the PIN diode of the double-tuned birdcage coil 70. The value of the control current 51 flowing to 30 is set to 0, and the DC control current 51 is applied so that the PIN diode 31 of the double tuning loop coil 71 is turned on.

By applying a control current 51 in double-tuned loop coil 71, PIN diode 31 is turned on, and the resonant parallel resonant circuit 55 consisting of capacitor 26 and inductor 16. is at the resonance frequency _{f 1,} the capacitor 27 and the inductor 17 parallel resonant circuit 56 resonates at the resonance frequency f ₂ made of. As a result, the impedance of the double-tuned loop coil 71 is extremely high, and almost no current flows through the double-tuned loop coil 71 and almost no magnetic field is generated.

On the other hand, in the double-tuned birdcage coil 70, the value of the control current 51 flowing through the diode 30 is 0, so that all the diodes 30 are turned off, and the parallel resonant circuit 54 has two capacitors 26 and 27 connected in series. The circuit is equivalent to a parallel circuit in which the inductor 18 is connected in parallel (trap circuit), and the double-tuned birdcage coil 70 resonates at the resonance frequency f ₁ and the resonance frequency f ₂ .

Therefore, the magnetic coupling between the double-tuned birdcage coil 70 and the double-tuned loop coil 71 is eliminated, and the double-tuned birdcage coil 70 can resonate without moving the resonance frequency due to the magnetic coupling or lowering the Q value of the coil. The inspection object 103 can be irradiated with a high-frequency magnetic field having the frequency f ₁ or f ₂ .

  When a magnetic resonance signal emitted from the inspection object 103 is received after applying the high frequency magnetic field, the magnetic coupling prevention circuit driving device 115 sets the control current 51 so that the diode 30 of the double tuning birdcage coil 70 is turned on. The value of the control current 51 applied to the diode 31 of the double tuning loop coil 71 is set to zero.

By applying a control current 51 double tuned birdcage coil 70, diode 30 is turned on, and the resonant parallel resonant circuit 130 consisting of a capacitor 26 and an inductor 16. is at the resonance frequency f _1, the capacitor 27 and the inductor 17 parallel resonance circuit 131 resonates at the resonance frequency _{f 2} made of. As a result, the impedance of the double-tuned birdcage coil 70 is extremely high at the resonance frequencies f ₁ and f ₂ , so that almost no current flows through the double-tuned birdcage coil 70 and no magnetic field is generated.

On the other hand, in the double-tuned loop coil 71, the value of the control current 51 flowing through the diode 31 is 0, so the diode 31 is turned off, and the connection between the inductor 16 and the capacitor 26 and the connection between the inductor 17 and the capacitor 27 are disconnected. As a result, the double-tuned loop coil 71 becomes a circuit equivalent to the double-tuned loop coil 150 of the first embodiment, and operates as a coil that resonates at the resonance frequencies f ₁ and f ₂ .

Therefore, when two magnetic resonance signals corresponding to the resonance frequency f ₁ or f ₂ emitted from the inspection object 103 are received, the magnetic coupling between the double-tuned birdcage coil 70 and the double-tuned loop coil 71 is lost. The double-tuned loop coil 71 receives a magnetic resonance signal corresponding to the resonance frequency f ₁ or f ₂ with high sensitivity without moving the resonance frequency due to magnetic coupling or lowering the Q value of the coil.

  As described above, according to the present embodiment, the double-tuned birdcage RF coil 70 and the double-tuned loop coil 71 that are tuned to two magnetic resonance frequencies close to each other when a high-frequency magnetic field is applied and when a magnetic resonance signal is received. And mutual magnetic coupling can be prevented. As a result, the double-tuned birdcage RF coil 70 transmits a uniform high-frequency magnetic field signal having two types of magnetic resonance frequencies close to each other, and the double-tuned loop coil 71 has high sensitivity to two types of magnetic resonance signals close to each other. And can be received simultaneously.

  Therefore, according to the present embodiment, the shape of the transmission RF coil 116a and the shape of the reception RF coil 116b can be selected independently. According to this embodiment, in addition to the effect which 1st embodiment has, the effect by the shape of RF coil 116 is acquired. For example, by using a double-tuned birdcage type coil 70 with high uniformity of irradiation distribution as the transmission RF coil 116a, and selecting the shape of the reception RF coil 116b according to the shape and size of the inspection object 103, each individual The magnetic resonance image optimized for the inspection object 103 can be taken. Of course, the transmitting RF coil 116 a is not limited to the double-tuned birdcage RF coil 70.

  In the present embodiment, a double-tuned array coil 72 as shown in FIG. 17 can be used as the reception RF coil 116b. The double-tuned array coil 72 is composed of a plurality of (four in FIG. 17) loop coils 1 that partially overlap each other. The overlapping position of the adjacent loop coils 1 is adjusted so that the magnetic coupling between the loop coils 1 is eliminated. By using the double tuning array coil 72, it is possible to image a wider area than when using a single receiving double tuning coil 71. Therefore, for example, two types of magnetic resonance signals that are close to each other can be simultaneously received with high sensitivity over the entire trunk of the subject (patient) that is the examination target 103.

  The magnetic coupling prevention circuit 68 is not limited to the above configuration. For example, the configuration shown in FIG. In the magnetic coupling prevention circuit 69 shown in FIG. 16C, two PIN diodes having different polar directions are used instead of the magnetic coupling prevention circuit driving device 115 provided in the magnetic coupling circuit 68 and the PIN diode driven thereby. A combined cross diode 34 is provided. A capacitor 26 and a capacitor 27 are connected in series. The capacitor 26 is connected in parallel with a circuit in which the cross diode 34 and the inductor 16 are connected in series. The capacitor 27 is connected in parallel with a circuit in which the cross diode 34 and the inductor 17 are connected in series. Yes.

Immediately before the high-frequency magnetic field having the resonance frequency f ₁ or f ₂ is applied from the high-frequency magnetic field generator 106 to the double-tuned birdcage coil 70, the magnetic coupling prevention circuit driving device 115 performs the PIN diode of the double-tuned birdcage coil 70. The value of the control current 51 flowing through 30 is set to 0.

In the double-tuned birdcage coil 70, the value of the control current 51 flowing through the diode 30 is 0, so that all the diodes 30 are turned off, and the parallel resonant circuit 54 includes a circuit in which two capacitors 26 and 27 are connected in series. Thus, the circuit is equivalent to a parallel circuit in which the inductors 18 are connected in parallel (trap circuit), and the double-tuned birdcage coil 70 resonates at the resonance frequency f ₁ and the resonance frequency f ₂ .

On the other hand, the double tuning loop coil 71 to which the high frequency magnetic field is applied generates a large electromotive force due to magnetic coupling, the cross diode 34 is turned on, and the parallel resonance circuit 57 including the capacitor 26 and the inductor 16 has a resonance frequency f. resonates at _1, the parallel resonance circuit 58 consisting of capacitor 27 and inductor 17. resonates at the resonance frequency _{f 2.} As a result, the impedance of the double-tuned loop coil 71 is extremely high, and almost no current flows through the double-tuned loop coil 71 and almost no magnetic field is generated.

Therefore, the magnetic coupling between the double-tuned birdcage coil 70 and the double-tuned birdcage coil 71 is eliminated, and the double-tuned birdcage coil 70 can be operated without moving the resonance frequency due to the magnetic coupling or lowering the Q value of the coil. The inspection object 103 can be irradiated with a high-frequency magnetic field having a resonance frequency f ₁ or f ₂ .

  When receiving a magnetic resonance signal emitted from the test object 103 after applying the high frequency magnetic field, the magnetic coupling prevention circuit driving device 115 applies the control current 51 to be supplied to the PIN diode 30 of the double tuning birdcage coil 70.

By applying a control current 51 double tuned birdcage coil 70, diode 30 is turned on, and the resonant parallel resonant circuit 130 consisting of a capacitor 26 and an inductor 16. is at the resonance frequency f _1, the capacitor 27 and the inductor 17 parallel resonance circuit 131 resonates at the resonance frequency _{f 2} made of. As a result, the impedance of the double-tuned birdcage coil 70 becomes extremely high at the resonance frequencies f ₁ and f ₂ , and no current flows through the double-tuned birdcage coil 70 and no magnetic field is generated.

On the other hand, the double-tuned loop coil 71 receives a magnetic resonance signal generated from the inspection object 103. However, since the magnetic resonance signal is an extremely small current, the cross diode 34 is turned off and the inductor 16 and the inductor 17 are not connected. As a result, the double-tuned loop coil 71 becomes a circuit equivalent to the double-tuned loop coil 150 of the first embodiment, and operates as a coil that resonates at the resonance frequencies f ₁ and f ₂ .

  As described above, when the magnetic coupling prevention circuit 69 is used, the reception double tuning coil does not use the magnetic coupling prevention circuit driving device 115, and the transmission double tuning birdcage RF coil 70 and the reception double tuning coil 71 are used. And magnetic coupling can be prevented. Therefore, in addition to the effect obtained when the magnetic coupling prevention circuit 68 is used, there is an effect that the configuration can be further simplified.

<< Fourth Embodiment >>
Next, a fourth embodiment to which the present invention is applied will be described. The MRI apparatus of this embodiment is basically the same as that of each of the above embodiments. In this embodiment, similarly to the second embodiment, the transmission / reception RF coil 116 is used by combining two double-tuned loop coils 150 of the first embodiment. However, in this embodiment, the loop surfaces of the two double tuning loop coils are installed in the same plane. Hereinafter, a configuration different from the second embodiment will be described.

  FIG. 18 is a diagram for explaining the transmission / reception RF coil 116 according to the present embodiment. The z-axis direction of coordinate 9 in the figure is the static magnetic field direction. As shown in the figure, the transmission / reception RF coil 116 of this embodiment includes a first double-tuned loop coil 59 and a second double-tuned loop coil 60. The configuration of each double-tuned loop coil 59, 60 is the same as that of the double-tuned loop coil 150 of the first embodiment. Furthermore, each of the first double-tuned loop coil 59 and the second double-tuned loop coil 60 of the present embodiment has two different resonance frequencies, similar to the double-tuned loop coil 150 of the first embodiment. It is adjusted to resonate.

  The loop surface 173 of the first double-tuned loop coil 59 of the transmission / reception RF coil 116 of this embodiment is disposed on a plane parallel to the xz plane of the coordinate 9. The loop surface 174 of the second double-tuned loop coil 60 is installed in the same plane as the loop surface 173 of the first double-tuned loop coil 59. The second double-tuned loop coil 60 is disposed inside the first double-tuned loop coil 59 and is adjusted to resonate at two resonance frequencies different from those of the first double-tuned loop coil 59. Yes. Further, in order to prevent magnetic coupling with the second double-tuned loop coil 60, the first double-tuned loop coil 59 includes two loops in which the second double-tuned loop coil is tuned in series. A parallel resonant circuit 35 and a parallel resonant circuit 36 each adjusted to a frequency are inserted. On the other hand, the second double-tuned loop coil has two frequencies at which the first double-tuned loop coil is tuned in series with the loop coil to prevent magnetic coupling with the first double-tuned loop coil. The adjusted parallel resonance circuit 37 and the parallel resonance circuit 38 are connected.

Hereinafter, the operation of the transmission / reception RF coil 116 of the present embodiment will be described. Here, the first double-tuned loop coil 59 has inductors 11, 12, 13 that resonate at ¹ H and ¹⁹ F (first resonance frequency f ₁ and second resonance frequency f ₂ , respectively). And the capacitors 21, 22, and 23 are adjusted, and the second double-tuned loop coil 60 includes ²³ Na (sodium) and ¹³ C (carbon) (the third resonance frequency f ₃ and the fourth resonance frequency f ₄ , respectively). The case where the inductors 81, 82, 83 and the capacitors 91, 92, 93 are adjusted so as to resonate will be described as an example.

When a signal having the _first resonance frequency f ₁ is transmitted to the first double-tuned loop coil 59, or when a signal having the first resonance frequency f ₂ is received by the first double-tuned loop coil 59 ( The parallel resonance circuit 37 inserted in series in the loop coil of the second double-tuned loop coil 60 is adjusted so as to resonate at the _first resonance frequency f _1. Therefore, the impedance becomes extremely high. On the other hand, if the first double-tuned loop coil 59 is tuned to the second resonance frequency f _2, the parallel resonant circuit 38 which is inserted in series with the loop of the second double-tuned loop coil 60, the second Since the resonance frequency f ₂ is adjusted so as to resonate, the impedance becomes extremely high. Therefore, regardless of the frequency (f ₁ , f ₂ ) of the first double-tuned loop coil 59, the first double-tuned loop coil 59 and the second double-tuned loop coil 60 are used. And the first double-tuned loop coil 59 has the first or second resonance frequency (f ₁ , f ₂ ) without moving the resonance frequency due to magnetic coupling or lowering the Q value of the coil. The high frequency magnetic field can be irradiated to the inspection object 103 and detected.

Similarly, when the second double-tuned loop coil 60 is tuned to the third resonance frequency f _3, the parallel resonance circuit 35 is serially inserted into the loop of the first double-tuned loop coil 59, first Since the resonance frequency f ₃ is adjusted so as to resonate, the impedance becomes extremely high. On the other hand, when the second double-tuned loop coil 60 tunes in the fourth resonance frequency f _4, the parallel resonance circuit 36 is serially inserted into the loop of the first double-tuned loop coil 59, a fourth Therefore, the impedance is extremely high. Accordingly, regardless of the frequency (f ₃ , f ₄ ) of the second double-tuned loop coil 60, the first double-tuned loop coil 59 and the second double-tuned loop coil 60 are used. And the second double-tuned loop coil 60 has the third or fourth resonance frequency (f ₃ , f ₄ ) without moving the resonance frequency due to the magnetic coupling or lowering the Q value of the coil. The high frequency magnetic field can be irradiated to the inspection object 103 and detected.

  As described above, according to the present embodiment, the double-tuned loop coil 59 and the double-tuned loop coil 60 that respectively tune to two magnetic resonance frequencies close to each other when a high-frequency magnetic field is applied and when a magnetic resonance signal is received. Can prevent mutual magnetic coupling. For this reason, according to this embodiment, it becomes possible to acquire signals of four resonance frequencies, and in addition to the effects of the first embodiment, it is possible to image various nuclides without exchanging coils.

  In each of the above embodiments, the second series resonance circuit 42, the third series resonance circuit 43, and the signal processing circuit 45 may be covered with the radio wave shield 52. Hereinafter, the configuration and operation in the case of covering with the radio wave shield 52 will be described by taking the double-tuned loop coil 150 of the first embodiment as an example.

  FIG. 19 is a diagram for explaining a case where the radio wave shield 52 is applied to the double-tuned loop coil of the first embodiment. As shown in the figure, here, the second series resonance circuit 42, the third series resonance circuit 43, and the signal processing circuit 45 of the double tuning loop coil 150 are covered with a radio wave shield 52. The radio wave shield 52 is grounded. The signal processing circuit 45 is connected to the signal line 53.

  Since the second series resonance circuit 42, the third series resonance circuit 43, and the signal processing circuit 45 are covered with the radio wave shield 52, the second series resonance circuit 42, the third series resonance circuit 43, and the signal processing are processed. The influence of the high frequency magnetic field generated in the loop of the circuit 45 on the high frequency magnetic field generated in the loop coil 1 can be reduced. For this reason, according to the present embodiment, it is possible to irradiate the subject 103 with a high-frequency magnetic field while suppressing disturbance of the magnetic field generated in the loop coil 1. The radio wave shield 52 can prevent magnetic coupling between the second series resonance circuit 42, the third series resonance circuit 43, the signal processing circuit 45, and the inspection target 103. That is, according to this embodiment, the influence of external noise can be reduced and loss due to magnetic coupling can be reduced.

It is a general-view figure of the MRI apparatus of 1st embodiment. It is a block diagram of the MRI apparatus of 1st embodiment. It is a circuit diagram of the double tuning loop coil of 1st embodiment. It is a figure for demonstrating operation | movement of the double tuning loop coil of 1st embodiment. It is a figure for demonstrating operation | movement of a general series resonance circuit. The resonance frequency f _B of the first _embodiment, is a diagram for explaining a method of determining the f _C. It is a circuit diagram of the double tuning saddle type coil of the first embodiment. It is a circuit diagram of the double tuning butterfly coil of the first embodiment. It is a circuit diagram of the double tuning solenoid coil of 1st embodiment. It is a circuit diagram of the triple tuned loop coil of 1st embodiment. It is a figure for demonstrating operation | movement of the triple tuning loop coil of 1st embodiment. It is a circuit diagram of the RF coil for transmission / reception of 2nd embodiment. It is a figure which shows the example of a connection of RF coil for transmission / reception of 2nd embodiment. It is a figure which shows the connection relation of RF coil of 3rd embodiment. It is a circuit diagram of the double tuning birdcage type | mold RF coil of 3rd embodiment. It is a circuit diagram of the double tuning loop coil of 3rd embodiment. It is a circuit diagram of the double tuning array coil of 3rd embodiment. It is a figure which shows the example of a connection of the double tuning loop coil of 4th embodiment. It is the schematic diagram which attached the electromagnetic wave shield to the double tuning loop coil of 1st embodiment. It is a circuit which shows the structure of the conventional double tuned RF coil. It is a circuit which shows the structure of the conventional double tuned saddle type RF coil.

Explanation of symbols

1: loop coil, 2: loop coil, 5: port, 6: port, 7: straight conductor, 8: loop conductor, 9: coordinate axis, 11: inductor, 12: inductor, 13: inductor, 14: inductor, 15: Inductor 16: Inductor 17: Inductor 18: Inductor 19: Inductor 21: Capacitor 22: Capacitor 23: Capacitor 24: Capacitor 25: Capacitor 26: Capacitor 27: Capacitor 29: Capacitor 30: PIN diode, 31: PIN diode, 34: cross diode, 35: parallel resonant circuit, 36: parallel resonant circuit, 37: parallel resonant circuit, 38: parallel resonant circuit, 40: series resonant circuit, 41: series resonant circuit 41 ': series resonance circuit, 42: series resonance circuit, 43: series resonance circuit, 44 Series resonant circuit, 45: signal processing circuit, 46: balun, 47: signal amplifier, 48: phase adjuster, 49: synthesizer, 50: distributor, 51: control signal line, 52: radio wave shield, 53: signal 54: magnetic coupling prevention circuit, 55: parallel resonance circuit, 56: parallel resonance circuit, 57: parallel resonance circuit, 58: parallel resonance circuit, 59: first double tuning coil, 60: second double coil Tuning coil, 61: first double tuning coil, 62: second double tuning coil, 63: direction of magnetic field generated by the first double tuning coil, 64: second double tuning coil is generated 65: first pickup coil, 66: second pickup coil, 68: first magnetic coupling prevention circuit, 69: second magnetic coupling prevention circuit, 70: double-tuned birdcage for transmission RF coil 71: Double tuning R for reception Coil, 72: Double tuned array coil for reception, 73: Apparent inductor, 74: Apparent inductor, 75: Apparent inductor, 76: Apparent capacitor, 77: Apparent capacitor, 78: Apparent capacitor, 81: Inductors 82: Inductors 83: Inductors 84: Apparent inductors 85: Apparent inductors 86: Apparent inductors 87: Apparent inductors 88: Apparent inductors 89: Apparent inductors 91: Capacitors 92: capacitor, 93: capacitor, 94: apparent capacitor, 95: apparent capacitor, 96: apparent capacitor, 97: apparent capacitor, 99: apparent capacitor, 99: apparent capacitor, 100: MRI apparatus, 101 : Mug that generates a static magnetic field Net: 102: Coil that generates a gradient magnetic field, 103: Inspection object, 104: Sequencer, 105: Gradient magnetic field power source, 106: High-frequency magnetic field generator, 107: RF coil for transmission, 108: Receiver, 109: Computer, 110 : Display, 111: Storage medium, 112: Shim coil, 113: Shim power source, 114: RF coil for reception, 115: Magnetic coupling prevention circuit driving device, 116: RF coil for transmission / reception, 130: Parallel resonance circuit, 131: Parallel resonance Circuit: 150: Double tuning loop coil, 151: Double tuning saddle coil, 152: Double tuning butterfly coil, 153: Double tuning solenoid coil, 154: Triple tuning loop coil, 155: QD system double Tuning loop coil, 171: first loop surface, 172: second loop surface, 173: first loop surface, 174: 2 loop surface, 200: MR device, 201: magnet for generating a static magnetic field, 301: table, 500: equivalent circuit, 501: equivalent circuit, 502: equivalent circuit, 600: equivalent circuit, 601: equivalent circuit, 602: Equivalent circuit, 603: Equivalent circuit

Claims (17)

A first series resonant circuit in which a capacitor is inserted into a loop coil made of a conductor;
A first circuit connected in parallel to the first series resonant circuit;
A magnetic field coil of a magnetic resonance imaging apparatus having a plurality of different resonance frequencies, and a signal processing circuit connected in parallel to the first circuit,
The first circuit includes a capacitor and an inductor, and a plurality of series resonance circuits having different resonance frequencies are connected in parallel,
The resonance frequency of each of the series resonance circuits is different from the resonance frequency of the first series resonance circuit,
The magnetic field coil of the magnetic resonance imaging apparatus, wherein each resonance frequency of the magnetic field coil is adjusted to be between the resonance frequencies of the first series resonance circuit and the series resonance circuit. A first series resonant circuit in which a capacitor is inserted into a loop coil made of a conductor;
A capacitor and an inductor connected in series, and a second series resonant circuit connected in parallel to the first series resonant circuit;
A capacitor and an inductor connected in series, and a third series resonant circuit connected in parallel to the second series resonant circuit;
A magnetic field coil of a magnetic resonance imaging apparatus comprising a signal processing circuit connected in parallel to the third series resonance circuit,
The first resonant frequency f of the first series resonant circuit resonant frequency f _A and the second series resonant circuit and the magnetic field transmitting and receiving coil and the resonant frequency f _C of the resonance frequency f _B third series resonant circuits of the ₁ and the second resonance frequency f ₂ are adjusted so as to satisfy the relationship of f _B <f ₁ <f _A <f ₂ <f _C. The loop coil includes two conductor loops arranged in correspondence with each other on the surface of a cylinder, and has a saddle shape connected so that directions of magnetic fields generated by the conductor loops are the same. The magnetic field coil according to claim 2. The loop coil includes two conductor loops arranged adjacent to each other in the same plane, and has a butterfly shape connected so that directions of magnetic fields generated by the conductor loops are opposite to each other. Item 3. The magnetic field coil according to Item 2. The magnetic field coil according to claim 2, wherein the loop coil has a solenoid shape. A fourth series resonance circuit connected in parallel between the third series resonance circuit and the signal processing circuit;
Each resonance frequency adds the resonance frequency f _D of the fourth series resonance circuit and the resonance frequency f ₃ (> f ₂ > f ₁ ) of the high-frequency magnetic field transmitting / receiving coil, and f _B <f ₁ <f _A <f _{2 <f C <f 3 <} f D _or claim 2, characterized in that it is adjusted so as to satisfy the relationship of _{f B <f 1 <f C} <f 2 <f a <f 3 <f D The magnetic field coil according to any one of 5. The magnetic field coil according to any one of claims 1 to 6, wherein a radio wave shield is applied to a portion other than the first series resonance circuit. The magnetic field coil according to any one of claims 2 to 5, wherein the first resonance frequency is 70% or more of the second resonance frequency. A first magnetic field coil;
A second magnetic field coil,
The first magnetic field coil is the magnetic field coil according to any one of claims 2 to 5,
The second magnetic field coil is the magnetic field coil according to any one of claims 2 to 5, wherein a magnetic field direction generated by the second magnetic field coil is orthogonal to a magnetic field direction generated by the first magnetic field coil. Arranged as
A magnetic field coil system for a magnetic resonance imaging apparatus, wherein a phase of a signal applied to the second magnetic field coil is 90 degrees different from a phase of a signal applied to the first magnetic field coil. A magnetic field coil system for a magnetic resonance apparatus, comprising: a plurality of array coils arranged on substantially the same plane so that the loop coil portions of the magnetic field coil partially overlap each other. A magnetic field transmission coil;
A magnetic field receiving coil;
Magnetic coupling prevention means,
The magnetic field transmission coils are magnetic field coils that operate at different resonance frequencies,
The magnetic field receiving coil is the magnetic field coil according to any one of claims 2 to 5, or the magnetic field coil system according to any one of claims 9 to 10.
The magnetic coupling prevention means opens the magnetic field receiving coil during signal transmission of the first resonance frequency and the second resonance frequency, and receives signals of the first resonance frequency and the second resonance frequency. Sometimes, the magnetic field transmission coil of the magnetic resonance imaging apparatus is characterized in that the magnetic field transmission coil is opened. The magnetic field coil system according to claim 10 or 11, wherein the magnetic coupling preventing means includes a diode, and the diode is turned on / off by an external control signal. The magnetic field coil system according to claim 11, wherein the magnetic coupling preventing unit includes a cross diode in which two diodes are connected in opposite directions. A first magnetic field transceiver coil;
A second magnetic field transceiver coil;
Magnetic coupling prevention means,
Said 1st magnetic field transmission / reception coil and said 2nd magnetic field transmission / reception coil are magnetic field coils of Claim 2, Comprising:
The two resonance frequencies of the second magnetic field transmission / reception coil are adjusted to be different from the two resonance frequencies of the first magnetic field transmission / reception coil,
The magnetic coupling preventing means opens the second magnetic field transmission / reception coil during signal transmission / reception of two resonance frequencies of the first magnetic field transmission / reception coil, and outputs signals of the two resonance frequencies of the second magnetic field transmission / reception coil. The magnetic field coil system of the magnetic resonance imaging apparatus, wherein the first magnetic field transmission / reception coil is opened during transmission / reception. A static magnetic field forming means for forming a static magnetic field, a gradient magnetic field forming means for forming a gradient magnetic field, a high frequency magnetic field forming means for forming a high frequency magnetic field, and applying the high frequency magnetic field to the inspection object to generate a magnetic resonance signal from the inspection object A magnetic resonance imaging apparatus comprising: a transmission / reception coil for receiving; and a control means for controlling the gradient magnetic field, the high-frequency magnetic field, and the transmission / reception coil,
The magnetic resonance imaging apparatus according to any one of claims 1 to 8, wherein the transmission / reception coil is the magnetic field coil according to any one of claims 1 to 8, or the magnetic field coil system according to any one of claims 9 to 10 and 14. Static magnetic field forming means for forming a static magnetic field, gradient magnetic field forming means for forming a gradient magnetic field, high-frequency magnetic field forming means for forming a high-frequency magnetic field, a transmission coil for applying the high-frequency magnetic field to an inspection object, and A magnetic resonance imaging apparatus comprising: a reception coil that receives a magnetic resonance signal; and a control unit that controls the gradient magnetic field, the high-frequency magnetic field, the transmission coil, and the reception coil,
The magnetic resonance imaging apparatus according to claim 1, wherein the transmission coil is the magnetic field coil according to claim 1, or the magnetic field coil system according to claim 9. Static magnetic field forming means for forming a static magnetic field, gradient magnetic field forming means for forming a gradient magnetic field, high-frequency magnetic field forming means for forming a high-frequency magnetic field, a transmission coil for applying the high-frequency magnetic field to an inspection object, and A magnetic resonance imaging apparatus comprising: a reception coil that receives a magnetic resonance signal; and a control unit that controls the gradient magnetic field, the high-frequency magnetic field, the transmission coil, and the reception coil,
The magnetic resonance imaging apparatus according to any one of claims 1 to 8, wherein the reception coil is the magnetic field coil according to any one of claims 1 to 8, or the magnetic field coil system according to any one of claims 9 to 10.

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